This invention relates to a device and method for spread-applying liquids, in particular glue over book spines.
As it is known, books, magazines, and pamphlets in general are coated with a glue over the spine region thereof prior to applying on them a protective outside cover which may have varying degrees of rigidity. Such a glue application step is of essential import to the strength and quality of the books or pamphlets, because of its primary contribution to holding the various parts thereof together. It is carried out in accordance with two basic techniques: contact spreading and spray application.
Contact spreading makes use of either rollers or brushes which, in contacting the spines of books or pamphlets, transfer the required glue thereto. Spray application utilizes spray nozzles which irrigate the spines of the books and are supplied with glue from specially provided pump members.
All of the aforesaid devices have disadvantages of considerable practical importance. Rollers and brushes tend to apply the glue in insufficient amounts where the spines happen to be uneven, the glue only depositing on the raised portions of the spines. Furthermore, rollers and brushes are required to match the shape of the spines to be coated, thereby they must be replaced each time that the type of pamphlet, book, or magazine varies. It should be also noted that in order to coat the book edges directly adjacent the book spines, as well as the spines proper, a plurality of rollers or brushes are to be provided which are arranged to be mutually perpendicular and define, accordingly, a device of relatively complex construction.
The devices utilizing spray nozzles tend, on the other hand, to irrigate the spines in an overabundant fashion, which not only results in a waste of glue but also in the glue running to soil parts of the books which are not intended to receive it. The problem cannot be obviated with current techniques, because while the glue is to be sprayed with some power, not all the glue can be made to adhere on the books and a part of it will tend to run unevenly from the spraying locations. Also specially difficult, with current techniques, is to confine the coating areas on which the nozzles or extruders are to act, where said areas include edges of the books adjacent the spines. And in all cases, said edges require the provision of specific extruders for the coating thereof.